One Berlin district has previously tried to legalise controlled marijuana dealing, but been thwarted by the Federal Institute for Drugs and Medical Devices.

The city is one of 16 federal states in Germany with the authority to introduce its own laws.

The move follows decriminalisation in Nevada, California and Massachusetts last week allowing over-21s to possess up to 28g (an ounce) of marijuana and grow up to six plants for personal use.

Max Plenert of the German Hemp Association, as quoted by broadcaster Deutsche Welle, said: "The legal code is decided at the federal level and this is about a local attempt to try to do things differently.

"This is a pilot project with limits. It's a chance to show politicians and the press that the topic isn't such a big deal. And that could kick-start larger changes.”

Britain's National Health Service says marijuana contains cancer-causing chemicals, is associated with psychotic illness including schizophrenia, can disrupt sperm production and ovulation, and can harm unborn babies.